TITANIUM-CARBON FUNCTIONALITIES ON AN OXO SURFACE DEFINED BY A CALIX[4]ARENE MOIETY AND ITS REDOX CHEMISTRY

Lithiation of [p-Bu-t-calix[4]-(OMe)(2)(OH)(2)] (1), followed by react ion with TiCl3(thf)(3) or TiCl4(thf)(2), led to the corresponding tita nium calix [4]arene complexes [p-Bu-t-calix[4]-(OMe)(2)(O)(2)TiCl] (2) and [p-Bu-t-calix [4] -(OMe)(2)(O)(2)TiCl2] (3), respectively. Reacti on of 1 with TiCl4(thf)(2) results in demethylation of the calix[4]are ne and the obtention of [p-Bu-t-calix[4]-(OMe) (O)(3)TiCl] (4),whose h ydrolysis led to [p-Bu-t-calix [4] -(OMe) (OH)(3)] (6), The preparatio n of 6 can be carried out as a one-pot synthesis. Both 2 and 4 undergo alkylation reactions using conventional procedures, thus forming surp risingly stable organometallic species, namely [p-Bu-t-calix [4]-(OMe) (2)-(O)(2)Ti(R)] (R =Me (7); CH2Ph(8),p-MeC6H4 (9)) and [p-Bu-t-calix[ 4] -(OMe) (O)(3)Ti(R)] (R =Me (10); CH2Ph (11);p-MeC6H4 (12)). Complex es 7 and 9 undergo a thermal oxidative conversion into 10 and 12, occu rring with the demethylation of one of the methoxy groups. A solid sta te structural property of 9 and 12 has been revealed by X-ray analysis showing a self-assembly of the monomeric units into a columnar polyme r, where the p-tolyl substituent at the metal functions as a guest gro up for an adjacent titanium-calixarene, Reductive alkylation of 3 with Mg(CH2Ph)(2) gave 8 instead of forming the corresponding dialkyl deri vative. Two synthetic routes have been devised for the synthesis of th e Ti(III)-Ti(III) dimer [p-Bu-t-calix[4]-(OMe)(O)(3)Ti](2)(13): the re duction of 4 and the reaction of TiCl3(thf)(3) with the lithiated form of 6. A very strong antiferromagnetic coupling is responsible for the peculiar magnetic behavior of 13. The proposed structures have been s upported by the X-ray analyses of 4, 9, 12 and 13. (C) 1998 Elsevier S cience S.A.